Melvin Manhoef against Robbie Lawler is a really good one.
I'm not sure about winning, I'd have to rewatch the fights, but I remember Chuck fighting on even terms with Rashad, Shogun, and Franklin before being KO'd.
Chael against Anderson is the ultimate one, and he had a habit of doing it throughout his career via great wrestling and poor submission defense.
Boxing, but Michael Moorer against Foreman. I had Moorer up 9-0 going into that 10th round.
Overeem does this all the fucking time. Bigfoot, Browne, Stipe. I'm sure I'm missing many more.
Machida. I had him winning the first round of Shogun II pretty handily before he got KO'd in that same first round. I had him up 1-0 against Jones before he got choked out in the second round, and got dropped like a hot potato.
That's all I got for now lol.